Three-dimensional integrated circuit (IC) device packages may include multiple semiconductor dies connected through an interposer die, which is then mounted on a package substrate. The semiconductor dies of the 3-D IC device may be located on the same plane or may be stacked on top of each other. Various configurations for 3-D IC devices may be realized, depending on the package type and functionality of the 3-D IC device.
In order to detect faulty components of the 3-D IC device, including the semiconductor dies and interposers, a technique known as thermography may be utilized. Thermography involves applying a voltage to the 3-D IC device and monitoring the thermal behavior of the device's components (e.g., semiconductor dies, interposer die). When a component of the semiconductor device includes faults, the temperature of that component will exhibit a temperature change in response to the applied voltage. The temperature change may be captured an infrared (IR) camera positioned facing the 3-D IC device, and the image used to determine the location of the fault in the X-Y plane.
With 3-D IC devices, simply locating the fault in the X-Y plane is not sufficient to isolate the location of the fault. For example, where multiple semiconductor dies and the interposer die are stacked on top of each other, the fault may be located in any of the semiconductor dies or the interposer die. Thus, it becomes necessary with 3-D IC devices to isolate the location of the fault by identifying a component (e.g., semiconductor dies or interposer die) of the 3-D IC device to which the fault belongs.
Conventional three-dimensional thermography fault isolation tools identify the component of the 3-D IC device to which the fault belongs by theoretically modeling the thermal behavior of the 3-D IC device. The theoretical thermal behavior model uses the various materials, thicknesses, and other parameters that make up the individual layers of components of the 3-D IC devices to model the time it takes for temperature of a component in the 3-D IC device to change in response to voltage being applied to the 3-D IC device. Whenever a fault is isolated in the X-Y direction by applying voltage to the 3-D IC device and capturing the temperature change with an IR camera, a time difference between the application of the voltage and the thermal change in the 3-D IC device is also determined. This time difference may then be compared against the theoretical thermal behavior model for the 3-D IC device to identify the component of the 3-D IC device to which the fault belongs.
While in theory using a theoretical thermal behavior model for a 3-D IC device should allow for accurate identification of the component of the 3-D IC device to which the fault belongs, in practice identification of the fault location using the theoretical thermal behavior model is often inaccurate. Although a theoretical thermal behavior model may be associated with a particular 3-D IC device type, each individual 3-D IC device of that type may exhibit thermal behavior that differs significantly from the theoretical model. This is due to the variability in material parameters during manufacturing of 3-D IC devices. For example, the thicknesses of layers making up components of an actual 3-D IC device may vary from the thicknesses of layers used to generate the theoretical model. Similarly, material parameters of solder bumps/balls forming connections between 3-D IC device components may also vary from the material parameters used to generate the theoretical model, leading to thermal behavior of the actual 3-D IC device that differs from the theoretical thermal behavior model.
Likewise because of the close proximity between components of the 3-D IC device, it is easy for a three-dimensional thermography fault isolation tool that utilizes a theoretical thermal behavior model to misidentify the component at which a fault is located based on time differences. Variability in 3-D IC device parameters from those of the theoretical model may cause enough of a change in time difference associated with temperature change for a faulty component, such that the thermal behavior model misidentifies the component at which the fault is located.
Because of such inaccuracies, conventional three-dimensional thermography fault isolation tools cannot be relied upon to isolate the location of the fault in a 3-D IC device.